FREDERICK, Md. - Potomac Appalachian Trail Club-West Chapter will conduct maintenance and complete placement of erosion control structures on the Yellow Poplar and Green Ash trails just above and below the trail head parking area. Meet at 10 a.m. at the Nature Center near the entrance to the High Knob day use area at Gambrill State Park, off U.S. 40 west of Frederick. For information, call Gambrill State Park at 301-293-4170 or e-mail ecreter@dnr.state.md.us.